Safety strip for a striking edge safety device or closing edge safety device

ABSTRACT

A safety strip for a striking edge protection device or closing edge protection device has contact elements arranged transversal to the longitudinal extension of the holding bodies, and the points of contact of the contact elements enable a flow of current from one side of one holding body to the other side of the other holding body. To this end, the holding bodies can be provided in the form of contact strips, spring brackets or the like, and sensors can be used instead of the contact elements. These sensors are mounted transversal to the longitudinal extension of the contact strips or of the spring bracket, and the sensors, via the operation thereof, actuate the electrical switching device.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a safety strip as a connecting block for astriking edge or closing edge protection device or switch pad with anelectrical switching device.

2. Description of the Prior Art

In EP 0 234 523 B1, which forms the class for the independent claims, isdescribed a striking edge protection device with a safety strip, whereinthe holding bodies (here called contact rollers) consist in each case ofcylindrical rollers, the contact rollers meeting each other in aproductive manner at the front-end points of contact. These holdingbodies display contact elements, which in the class-forming literaturepassage are described as sleeves consisting of copper or nickel silver.The holding bodies are acted on by an elastic prestress through the factthat arranged in the interior of the contact rollers is an elastic cordthat forces the individual contact rollers, and thus the holding bodies,in an axial direction against each other. Arranged between theindividual holding bodies are insulating rings, which are arrangedbetween the individual holding bodies with projecting wedge surfacesoriented radially with respect to the insulating-ring axis. In the eventof a force oriented preferably transversely with respect to thelongitudinal extension of the contact chain, only a minimum of wedgingeffect between the contact elements and the insulating ring results inan interruption of the closed-circuit current, which leads to aswitching function within the switching device. After unloading of thecontact chain, an automatic neutral position for closing theclosed-circuit current circuit occurs. For the sensitivity of theresponse, the degree position of the collaborating wedge surfaces isessential.

With this known apparatus it is scarcely possible to construct safetystrips that must be installed in a small radius, for example around acentral pipe, in order to serve as a striking protection device.

For this application case, the use of the spheres from FR 21 35 922 A5as contact elements is also not applicable. In this arrangement, thespheres do not center themselves in the soft hose, but rather, in orderto make way for the prestress generated through the hose, the spheresshift against each other, so that a straight-line sphere chain is notpresent in the installed state.

Characteristic of both of the arrangements belonging to the prior art isthe fact that a separation of the points of contact occurs in the caseof a striking load upon the safety strip in a direction transverse tothe longitudinal axis of the safety strip; for example, in the case ofEP 0 234 523 B1 the elastic cord is stretched and in the case of thedevice according to FR 21 35 922 A5 the elastic hose is elongated.

Described in EP 421048 B1 is a safety strip that is to be used as aswitch pad, wherein a multitude of contact elements and wedge elementsare provided that are pulled against each other by means of an elasticcord. The wedge elements are formed as wedge plates and the contactelements as contact plates, whereby in the switching-ready state theelastic cord lies at different heights in the contact plates and in thewedge plates.

SUMMARY OF THE INVENTION

The invention is based on the object of creating a safety strip that hashigh response sensitivity and can be installed in the smallest radiuses.A further goal is that the striking or closing edge protection device orswitch pad be producible in a more cost-effective manner than thedevices belonging to the prior art.

This object forming the basis of the invention is achieved through theteaching of the main claim.

Expressed in different words, according to the invention it is proposedthat the contact elements be arranged transversely to the longitudinalextension of the safety strip and, via their contact points, allow acurrent flow that preferably flows from one side of one holding body tothe other side of the other holding body.

The safety strip can, according to the invention, be designed as aspring bracket, where the legs of the bracket represent the holdingbodies. On the other hand, it is possible to design the holding bodiesas contact strips in which the contact elements, viewed over the lengthof the strip, are arranged at a distance from each other and areconnected in series via conductive means. Possible, finally, are contactstrips consisting of plastic and connected to each other via a hingestrip in a material-unified manner.

Viewed over the length of a safety strip, in the arrangement accordingto the invention fewer contact elements can be provided, since, byvirtue of the formation of the safety strips of dimensionally stablematerial, the action of the insulating wedge elements also lifts orpushes apart the strips over a wider region than is the case with thedevices according to the prior art, a current interruption neverthelessoccurring immediately.

Through appropriate construction, the arrangement according to theinvention can operate according to both the closer principle and theopener principle.

According to the invention, the contact strips can consist of adimensionally stable material as well as of a rubber-elastic material.

Likewise, the insulating wedge elements can consist of dimensionallystable material and the insulating wedge elements can be designed ascontinuous insulating wedge strips.

The holding bodies, i.e. the contact strips or spring bracket, can bearranged together with the insulating wedge elements or insulating wedgestrips in a receiving space that is enclosed by an outer housing wall.This outer housing wall can consist of elastic material as well as ofrigid material. The receiving space itself can be bounded by elasticwall elements, so that, on the one hand, a sufficient degree of givingway is possible, and on the other hand the elastic prestress for the twoholding bodies can be already achieved thereby.

It is likewise possible to apply the elastic prestress to the holdingbodies by means of separate elastic tensioning elements.

The use of elastic elements to produce the receiving space also makes itpossible for the contact strips or holding bodies, as the case may be,and the insulating wedge elements to be displaced transversely withrespect to the contact strip, so that thereby the incorporation of abraking or slowing-down path is possible.

The safety strip, i.e. the holding bodies and the insulating wedgeelements, can have a ringshaped form, can have a linear form, or displaypolygonal geometries. If the holding bodies and the insulating wedgeelements have a semicircular form, the combination of individual pieceelements in linear and circular manners is likewise possible.

The application field of the striking and closing edge protection deviceaccording to the invention is, among others, the securing of measuringarms on measuring machines and the securing of robot arms; applicationsas end-of-travel switches and as hinge switches are also possible.

Finally, according to the invention it is proposed that the holdingbodies be formed as a contact strip or spring bracket and receivesensors, the sensors extending transversely to the longitudinalextension of the contact strip or the spring bracket. The sensor actionaffects an electrical switching apparatus.

Understood as a sensor in the context of the present invention is acomponent that detects physical or chemical magnitudes and convertsthese into electrical or digital signals, and is consequently suitablefor measurement and switching. As sensors, photocells, optical fibers,ultrasound elements, magnetically active elements, or similar devicesbelonging to the prior art can be used.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, embodiment examples of the invention are explainedwith reference to the drawings. In the drawings:

FIG. 1: shows a section through a safety strip as a contact ring;

FIG. 2: shows a view of an elongated safety strip in section;

FIG. 3: shows a sectional representation at right angles to therepresentation corresponding to FIG. 2;

FIG. 4: shows a sectional representation through a modified design ofthe actual safety strip;

FIG. 5: shows a plan view of the safety strip that is shown installed inFIG. 1;

FIG. 6: shows diagrammatic view of a further embodiment form of aring-shaped safety strip;

FIG. 7: shows diagrammatically a safety strip wherein the holding bodyis designed as a spring bracket.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Represented in section in FIG. 1 is a safety strip S as a contact ringthat is placed around an inner pipe 11. This contact ring displays twoholding bodies arranged one above the other and formed as contact strips1, 2, which holding bodies in each case abut on each other with contactelements 3, 4, the contact elements 3 and 4 being formed of, forexample, tubular rivets. The contact elements 3, 4 abut each other atcontact points A and B. In the embodiment example represented in FIG. 1,placed into the contact elements 3 and 4 is a piece of elastic cord as aprestress element 6, which cord forces the two holding bodies, i.e. thecontact strips 1 and 2, against each other, so that the two contactelements 3, 4 abut each other and thus close the contact points A and B.

The two contact strips 1 and 2 are open toward the outside in awedge-shaped manner and inserted into this wedge space is an insulatingwedge element 5, which is covered toward the outside by a housing wall7. The contact strips 1 and 2 are situated in a receiving space 10, thisreceiving space 10, in the embodiment example according to FIG. 1, beingformed through horizontally-oriented wall elements 8 and 8 consisting ofpolyurethane foam and enclosing between themselves a wall element 9 thatlikewise consists of polyurethane foam, but which can display adifferent solidity than the wall elements 8 and 8. In the representedembodiment example according to FIG. 1, the housing wall 7 closing offthe receiving space 10 toward the outside consists of a relatively stiffmaterial, so that in the event of a impact on an obstacle this housingis moved inwardly toward the receiving space 10, which is possiblebecause the wall elements 8 and 8 can yield elastically. At the sametime, however, the wall element 9 forms a certain resistance, so thatthe insulating wedge element 5 can penetrate into the correspondingspace between the two contact strips 1 and 2 and cancel the contactbetween contact points A and B, thus causing a switching action.

FIG. 2 shows, in a cut-away manner, an arrangement of an elongatedsafety strip S. Here, the holding bodies are formed as contact strips 1and 2, the contact elements 3 and 4 are clearly recognizable, and inparticular FIG. 3 shows the wedge-shaped insulating wedge strip 5,pressure upon which now moves the two contact strips 1 and 2 apart andthereby the contact points A and B are separated. The means whereby inthe resting state the two contact strips 1 and 2 are forced against eachother are not represented in FIGS. 2 and 3, but the electricalconnections between the sequential contact elements are. Providedbetween the contact element 3 located at the center in FIG. 2 and thecontact element 3 located on the left is an electrical conductor 12 thatcan be designed in a manner belonging to the prior art.

In the representation in FIG. 2, the conductor 12 lies on the top sideof the contact strip 1. From the middle contact element 4 of the lowercontact strip 2 an electrical conductor 12 a leads to the lower contactelement 4 located on the right in the drawing, and from thisrepresentation it is evident that the individual contact elements areconnected in series, so that the current can flow from the left-locatedcontact element 3 to the contact element 3 located in the middle, thenvia the contact elements 3 and 4 reaches the lower side of the strip 2,and there flows via the conductor 12 a to the contact element 4 on theright side of the drawing, from where the current then flows again tothe contact element arranged on the contact strip 1 and from here, viathe electrical connection 12 shown in the drawing, to the next contactelement.

FIG. 4 shows an arrangement with two contact strips 1 and 2 and aninsulating wedge element 5, wherein, however, the two contact elements 1and 2 are firmly connected to each other, i.e. materially connected,through a hinge component 16. This hinge strip 16 can be designed as afilm strip, so that the two contact strips 1 and 2 are easily swung openor closed. However, it is also possible, as represented in FIG. 4, toform this hinge strip 16 relatively large, so that thereby the requiredprestress of the two contact strips 1 and 2 is already achieved.

In any case, such a material-united design of the contact strips 1 and 2offers a simplified production and operation possibility.

In the embodiment form according to FIG. 5, the electrical circuit isonce again made clear. FIG. 5 shows that a circular safety strip 5 candisplay, for example, six contact elements 3 and 4. In FIG. 5, whichshows a plan view of the upper contact strip 1, the upper contactelements 3 are visible. Represented by 14 is an electrical input linethat leads to contact element 3 of the upper contact strip 1. From here,viewed toward the right in the represented embodiment example, anelectrical conductor 12 leads to the contact element 3 of the uppercontact strip 1, and from here the current can flow via the uppercontact element 3 and the lower contact element 4 to the bottom of thelower contact strip 2. As shown in dashes at 12 a, an electricalconnection then takes place to the next contact element 4 of the lowercontact strip 2, and from here the current can flow upward via the uppercontact element 3 of the upper contact strip 1 and again reach anelectrical conductor 12.

Represented at 14 a is the return conductor of the current and it isevident that the individual contact elements 3 and 4 are connected inseries.

Since the contact strips 1 and 2 consist of rigid material, an impact onthe insulating wedge element 5 at any point suffices to cause a currentinterruption. However, let it be expressly pointed out that thearrangement according to the invention, which is represented in terms ofthe opener principle, can also operate according to the closerprinciple.

FIG. 6 shows a ring-shaped safety strip S with contact strips 1 and 2and, for reasons of clarity, without the insulating wedge strip 5,wherein the upper contact element 3 is recognizable in the plan view.The elastic prestress between the two contact strips 1 and 2 is producedin this embodiment form through tube pieces 15, but it should be pointedout that the elastic prestress by which the contact strips 1 and 2 arepressed against each other can be designed in any manner.

Thus, for example, the two contact strips can also be placed into arubber profile tube so that the profile is extruded, whereby, incontrast to the prior art, such a tube is no longer extended in lengthduring the operation of the insulating wedge strip, but rather thediameter of the tube is enlarged.

Finally, FIG. 7 shows in section a safety strip S with a U-shaped springbracket 101, the contact elements 3 and 4 being placed into the bracketlegs 102, 103. An insulating wedge element 104 reaches with its wedgesection between the ends of the bracket legs 102 and 103, which ends arewidened in a wedge-shaped manner, and thus causes the contact elements 3and 4 to move apart. Visible on the contact elements 3 and 4 are cablelugs 105 and 106, to which the corresponding current line 12 and 12 aconnect. In this case, the actual safety strip S can consist of metal,or, in like manner, can be produced as a molded plastic piece.

1. A safety strip comprising a switching strip for a striking edgeprotection device or closing edge protection device with an electricalswitching device, wherein the safety strip includes contact elementsarranged in holding bodies, wherein the contact elements in a restposition abut each other at contact points under effect of an elasticprestress and, under effect of an outside force on an insulating wedgeelement arranged between the holding bodies, can be moved apart so thatcontact is interrupted, wherein the contact elements are arranged in theholding bodies transversely to a longitudinal extension of the safetystrip and via the contact points make possible a current flow from oneside of one of the holding bodies to a side of the other holding body.2. Safety strip according to claim 1, wherein a) the safety strip isformed as an essentially U-shaped spring bracket, b) the contactelements are arranged transversely to bracket legs forming the holdingbodies and the contact points make possible a current flow, c) theinsulating wedge element acts on free ends of the spring bracket. 3.Safety strip according to claim 1, wherein the holding bodies are formedas contact strips.
 4. Safety strip according to claim 3, wherein thecontact strips are placed into a receiving space.
 5. Safety stripaccording to claim 4, wherein the receiving space is closed off throughan outer housing wall.
 6. Safety strip according to claim 5, wherein thehousing wall comprises elastic material.
 7. Safety strip according toclaim 5, wherein the housing wall comprises rigid material.
 8. Safetystrip according to claim 4, wherein the receiving space is bounded byelastic wall elements.
 9. Safety strip according to claim 1, furthercomprising another contact strip, wherein the contact strips compriseplastic and are connected in a material-unified manner by a hinge strip.10. Safety strip according to claim 9, wherein the contact stripsconsist of dimensionally stable material.
 11. Safety strip according toclaim 9, wherein the contact strips comprise rubber-elastic material.12. Safety strip according to claim 1, further comprising anothercontact strip, wherein contact elements are arranged in a spaced-apartmanner, viewed over the length of the safety strips.
 13. Safety stripaccording to claim 1, wherein the contact elements are connected inseries by an electrical conductor.
 14. Safety strip according to claim1, wherein the insulating wedge element comprises dimensionally stablematerial.
 15. Safety strip according to claim 1, wherein the insulatingwedge element is formed as an insulating wedge strip.
 16. Safety snipaccording to claim 1, wherein the elastic prestress for the holdingbodies is applied through elastic tension elements.
 17. A safety stripcomprising a switching strip for a striking edge protection device orclosing edge protection device with an electrical switching device,wherein the safety strip includes at least one holding body that carriesat least one sensor, that is acted upon by an elastic prestress in arest state, and that reacts to action of an outer force on insulatingwedge elements arranged between holding bodies, wherein a) each of theholding bodies is formed as a contact strip or spring bracket, b) and atleast one sensor is arranged transversely to a longitudinal extension ofthe safety strip or the spring bracket and actuates the electricalswitching device through sensor action.